Wet-soil redeposition has been recognized as a major source of soiling for a number of years. In simplified terms this phenomenon is the spreading-out of localized soil over the entire area of a textile product being cleaned or as sometimes happens the transfer of soil from a heavily soiled product onto a lightly soiled product during cleaning. There are certain generally accepted theories as to how redeposition occurs during laundering.
When soiled articles are placed in a landery machine with water and detergent, theoretically the soil is removed from the fabrics and dispersed by the detergent. The degree of soil removal from the fabric is dependent upon many factors, including water temperature, type and amount of soil, type and amount of detergent, and the chemical composition of the textile fibers being laundered. If the detergent present in the wash water is not functioning with the proper degree of efficiency, all of the soil will not be held in dispersion. In practical terms, this results in what can be described as a three-way equilibrium between soil remaining on the surface of the fabric, soil dispersed by the detergent and soil which is mechanically suspended in the wash water by the agitation forces of the laundry equipment. The laundry machine represents a dynamic system; this results in a general re-distribution of the soil not held in dispersion over the surfaces of the fabric in the wash load.
In an effort to overcome wet-soil redeposition, and especially wet-soil redeposition on cotton fiber containing fabrics, the detergent industry has incorporated certain additives such as for instance sodiumcarboxymethyl cellulose. Redeposition of soil in the detergent process consists essentially of the deposition of dispersed particulate soil which may be considered to be in a colloidal state onto a fabric in a detergent liquor. Colloidal properties arise from a large value for the ratio of surface area to mass, although this does not, of course, extend to molecular dimensions. Therefore, it is reasonable to consider that the fabric, with its very irregular surface and consequently large surface area, should also exhibit colloidal behaviour in a detergent bath. On the basis of the above assumption, soil redeposition may be considered as being equivalent to the coagulation of the colloidal dispersion and colloid stability theory therefore should be applicable. The system consisting of dispersed soil and fabric detergent liquor may be treated as a colloidal system. Colloid stability or soil redeposition is governed by the result of three component foreces: (1) an electrical force which may be either attractive or repulsive and that is due to a double layer interaction; ( 2) an attractive force that arises from the dispersion forces, and (3) a non-electrical repulsive force that is due to a non-electrical interaction of the surface adsorption layers of the particles. The ionogenic whiteness retention additives such as the sodium salt of carboxymethyl cellulose functions primarily by increasing the electrical repulsive force as a result of being adsorbed on soil and/or fabric. Carboxymethyl cellulose however, has not been proved to be suitable for incorporation into heavy duty liquid detergent mixtures, nor has carboxymethyl cellulose completely solved the soil redeposition problem in polyester fiber containing fabrics.
An increasing number of wearing apparel and other textile materials are fashioned from fabrics which are formed from synthetic fibers and from snythetic fiber/natural fiber blends. These textile materials are capable of being cleaned both by wet laundering and dry cleaning procedures.
In a conventional process of dry cleaning fabrics, the soiled fabrics are agitated in a volatile organic dry cleaning solvent which is relatively immiscible with water. Such solvents are generally effective for the removal of grease and oil stains as well as dust, dirt, lint and the like which commonly adhere to the fabrics and to the grease and oil thereon. The agitation is generally accomplished by inserting the fabrics into a perforated cylinder which is rotated in the solvent bath. The solvent is usually circulated by means of a pump through a filter which removes suspended soil particles. By means of recycling and filtering, the solvent can generally be reused many times, and after becoming badly contaminated, can be distilled and used again. After sufficient treatment, the fabrics are usually subjected to centrifugal action to remove excess solvent and then placed in a rotating cylinder or drying cabinet wherein final traces of solvent are removed by a current of warm air.
As a recent development, such as in the cleaning of work clothes, it is becoming common practice to first conduct a conventional dry cleaning procedure, and follow this by a conventional wet laundering procedure.
Heretofore there has not been considered the development of a dry cleaning system which would effectively dry clean textile material and concomitantly impart to the textile materials anti-soiling properties which in subsequent wet laundering procedures would act to prevent wet-soil redeposition and improve stain-release characteristics of the laundered textile materials.
Accordingly, it is an object of the present invention to provide an improved dry cleaning solvent system.
It is another object of the present invention to provide a process for improving the anti-soil characteristics of textile materials.
It is a further object of the present invention to provide a method of treating textile materials so as to prevent wet-soil redeposition and improve stain-release properties when the textile materials are subjected to repeated wet laundering.
Other objects and advantages shall become apparent by the following description and example.